Slow-roll Inflation for Generalized Two-Field Lagrangians

We study the slow-roll regime of two field inflation, in which the two fields are also coupled through their kinetic terms. Such Lagrangians are motivated by particle physics and by scalar-tensor theories studied in the Einstein frame. We compute the power spectra of adiabatic and isocurvature perturbations on large scales to first order in the slow-roll parameters. We discuss the relevance of the extra coupling terms for the amplitude and indexes of the power spectra. Beyond the consistency condition which involves the amplitude of gravitational waves, additional relations may be found in particular models based on such Lagrangians: as an example, we find an additional general consistency condition in implicit form for Brans-Dicke theory in the Einstein frame.Comment: 17 pages, 1 figure, accepted for publication in Phys. Rev.

Evolution of Large Scale Curvature Fluctuations During the Perturbative Decay of the Inflaton

We study the evolution of cosmological fluctuations during and after inflation driven by a scalar field coupled to a perfect fluid through afriction term. During the slow-roll regime for the scalar field, the perfect fluid is also frozen and isocurvature perturbations are generated. After the end of inflation, during the decay of the inflaton, we find that a change in the observationally relevant large scale curvature fluctuations is possible.Comment: 9 pages, 2 figures; v2: version published in PR

Phase-change chalcogenide glass metamaterial

Combining metamaterials with functional media brings a new dimension to their performance. Here we demonstrate substantial resonance frequency tuning in a photonic metamaterial hybridized with an electrically/optically switchable chalcogenide glass. The transition between amorphous and crystalline forms brings about a 10% shift in the near-infrared resonance wavelength of an asymmetric split-ring array, providing transmission modulation functionality with a contrast ratio of 4:1 in a device of sub-wavelength thickness.Comment: 3 pages, 3 figure

Photon recycling in Fabry-Perot micro-cavities based on Si3_3N4_4 waveguides

We present a numerical analysis and preliminary experimental results on one-dimensional Fabry-Perot micro-cavities in Si$_3$N$_4$ waveguides. The Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors separated by a straight portion of waveguide. The Bragg reflectors are composed by a few air slits produced within the Si$_3$N$_4$ waveguides. In order to increase the quality factor of the micro-cavities, we have minimized, with a multiparametric optimization tool, the insertion loss of the reflectors by varying the length of their first periods (those facing the cavity). To explain the simulation results the coupling of the fundamental waveguide mode with radiative modes in the Fabry-Perot micro-cavities is needed. This effect is described as a recycling of radiative modes in the waveguide. To support the modelling, preliminary experimental results of micro-cavities in Si$_3$N$_4$ waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure

Ataxia with oculomotor apraxia type 2: a clinical, pathologic, and genetic study

BACKGROUND: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by onset between age 10 and 22 years, cerebellar atrophy, peripheral neuropathy, oculomotor apraxia (OMA), and elevated serum alpha-fetoprotein (AFP) levels. Recessive mutations in SETX have been described in AOA2 patients. OBJECTIVE: To describe the clinical features of AOA2 and to identify the SETX mutations in 10 patients from four Italian families. METHODS: The patients underwent clinical examination, routine laboratory tests, nerve conduction studies, sural nerve biopsy, and brain MRI. All were screened for SETX mutations. RESULTS: All the patients had cerebellar features, including limb and truncal ataxia, and slurred speech. OMA was observed in two patients, extrapyramidal symptoms in two, and mental impairment in three. High serum AFP levels, motor and sensory axonal neuropathy, and marked cerebellar atrophy on MRI were detected in all the patients who underwent these examinations. Sural nerve biopsy revealed a severe depletion of large myelinated fibers in one patient, and both large and small myelinated fibers in another. Postmortem findings are also reported in one of the patients. Four different homozygous SETX mutations were found (a large-scale deletion, a missense change, a single-base deletion, and a splice-site mutation). CONCLUSIONS: The clinical phenotype of oculomotor apraxia type 2 is fairly homogeneous, showing only subtle intrafamilial variability. OMA is an inconstant finding. The identification of new mutations expands the array of SETX variants, and the finding of a missense change outside the helicase domain suggests the existence of at least one more functional region in the N-terminus of senataxin

Strong Correlations in a nutshell

We present the phase diagram of clusters made of two, three and four coupled Anderson impurities. All three clusters share qualitatively similar phase diagrams that include Kondo screened and unscreened regimes separated by almost critical crossover regions reflecting the proximity to barely avoided critical points. This suggests the emergence of universal paradigms that apply to clusters of arbitrary size. We discuss how these crossover regions of the impurity models might affect the approach to the Mott transition within a cluster extension of dynamical mean field theory.Comment: 45 pages, 14 figures. To appear in Journal of Physics: Condensed Matte

Surface enhanced Raman scattering substrate based on gold-coated anodic porous alumina template

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Effect of the Orbital Level Difference in Doped Spin-1 Chains

Doping of a two-orbital chain with mobile S=1/2 Fermions and strong Hund's rule couplings stabilizing the S=1 spins strongly depends on the presence of a level difference among these orbitals. By DMRG methods we find a finite spin gap upon doping and dominant pairing correlations without level-difference, whereas the presence of a level difference leads to dominant charge density wave (CDW) correlations with gapless spin-excitations. The string correlation function also shows qualitative differences between the two models.Comment: 4 pages, 4 figure

First-trimester choroid-plexus-to-lateral-ventricle disproportion and prediction of subsequent ventriculomegaly.

OBJECTIVE: Ventriculomegaly can be associated with long-term neurodevelopmental impairment. Prenatal diagnosis of ventriculomegaly is most commonly made at the routine second-trimester anomaly scan. The value of first-trimester ultrasound has expanded to early diagnosis and screening of fetal abnormalities. The objective of this study was to assess the predictive accuracy of first-trimester choroid-plexus-to-lateral-ventricle-or-head ratios for development of ventriculomegaly at a later gestational age. METHODS: This was a case-control study of fetuses with isolated ventriculomegaly diagnosed after 16 weeks' gestation and a control group of normal fetuses (without ventriculomegaly). The exclusion criteria included aneuploidy, genetic syndrome and/or other brain abnormality. Stored two-dimensional first-trimester ultrasound images were analyzed blindly offline and fetal biometry was performed in the axial view of the fetal head. The ratios of choroid plexus area (PA) to lateral ventricular area (VA), choroid plexus length (PL) to lateral ventricular length (VL), choroid plexus diameter (PD) to lateral ventricular diameter (VD) and PA to biparietal diameter (BPD) were measured at 11 + 0 to 13 + 6 weeks' gestation. Intra- and interobserver variability of measurement of these fetal head biometric parameters at 11 + 0 to 13 + 6 weeks' gestation were assessed in 20 normal fetuses using intraclass correlation coefficients with 95% CI. The accuracy of first-trimester biometric measurements for prediction of ventriculomegaly was assessed using the area under the receiver-operating-characteristics curves (AUC). RESULTS: The analysis included 683 singleton pregnancies, of which 102 fetuses were diagnosed with ventriculomegaly. Ventriculomegaly was mild in 86 (84.3%) cases and severe in the other 16 (15.7%). All first-trimester fetal choroid-plexus-to-lateral-ventricle/head ratios were significantly lower in cases with ventriculomegaly compared with controls (P < 0.001), with good inter- and intraobserver agreement (≥ 0.95) for the majority of the fetal head biometric parameters assessed. On adjusting for crown-rump length, optimism-adjusted AUC values obtained after cross-validation showed that both PL/VL ratio (AUC, 0.87 (95% CI, 0.73-0.98)) and PA/VA ratio (AUC, 0.90 (95% CI, 0.82-0.98)) had good predictive accuracy for severe ventriculomegaly. The PA/BPD ratio (AUC, 0.73 (95% CI, 0.54-0.90)) had modest predictive ability, which was significantly lower compared with that of the PA/VA ratio and PL/VL ratio (P = 0.003 and P = 0.001, respectively). The predictive accuracy of PD/VD ratio was low with an AUC of 0.65 (95% CI, 0.47-0.84). Optimism-adjusted AUC values obtained after cross-validation showed that PA/VA ratio offered the highest predictive accuracy for mild ventriculomegaly with an AUC of 0.84 (95% CI, 0.79-0.89), followed by PL/VL ratio (AUC, 0.82 (95% CI, 0.76-0.88)), PA/BPD ratio (AUC, 0.76 (95% CI, 0.69-0.82)) and PD/VD ratio (AUC, 0.75 (95% CI, 0.67-0.81)). Calibration plots showed that both PA/VA and PL/VL ratios had good calibration. CONCLUSION: First-trimester prediction of ventriculomegaly using ratios of fetal choroid plexus to lateral ventricle/head appears promising. Future prospective studies are needed to validate the predictive accuracy of these ultrasound markers as a screening tool for ventriculomegaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology

Nano-topography Enhances Communication in Neural Cells Networks

Abstract Neural cells are the smallest building blocks of the central and peripheral nervous systems. Information in neural networks and cell-substrate interactions have been heretofore studied separately. Understanding whether surface nano-topography can direct nerve cells assembly into computational efficient networks may provide new tools and criteria for tissue engineering and regenerative medicine. In this work, we used information theory approaches and functional multi calcium imaging (fMCI) techniques to examine how information flows in neural networks cultured on surfaces with controlled topography. We found that substrate roughness S a affects networks topology. In the low nano-meter range, S a  = 0–30 nm, information increases with S a . Moreover, we found that energy density of a network of cells correlates to the topology of that network. This reinforces the view that information, energy and surface nano-topography are tightly inter-connected and should not be neglected when studying cell-cell interaction in neural tissue repair and regeneration